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(#) Using `dp` instead of `sp` for text sizes

!!! WARNING: Using `dp` instead of `sp` for text sizes
   This is a warning.

Id
:   `SpUsage`
Summary
:   Using `dp` instead of `sp` for text sizes
Severity
:   Warning
Category
:   Correctness
Platform
:   Android
Vendor
:   Android Open Source Project
Feedback
:   https://issuetracker.google.com/issues/new?component=192708
Since
:   Initial
Affects
:   Resource files
Editing
:   This check runs on the fly in the IDE editor
See
:   https://developer.android.com/training/multiscreen/screendensities.html
Implementation
:   [Source Code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-checks/src/main/java/com/android/tools/lint/checks/PxUsageDetector.java)
Tests
:   [Source Code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-tests/src/test/java/com/android/tools/lint/checks/PxUsageDetectorTest.java)
Copyright Year
:   2011

When setting text sizes, you should normally use `sp`, or
"scale-independent pixels". This is like the `dp` unit, but it is also
scaled by the user's font size preference. It is recommend you use this
unit when specifying font sizes, so they will be adjusted for both the
screen density and the user's preference.

There **are** cases where you might need to use `dp`; typically this
happens when the text is in a container with a specific dp-size. This
will prevent the text from spilling outside the container. Note however
that this means that the user's font size settings are not respected, so
consider adjusting the layout itself to be more flexible.

!!! Tip
   This lint check has an associated quickfix available in the IDE.

(##) Example

Here is an example of lint warnings produced by this check:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~text
res/layout/textsize.xml:11:Warning: Should use "sp" instead of "dp" for
text sizes [SpUsage]
    android:textSize="14dp" /&gt;
    -----------------------
res/layout/textsize.xml:16:Warning: Should use "sp" instead of "dp" for
text sizes [SpUsage]
    android:textSize="14dip" /&gt;
    ------------------------
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Here is the source file referenced above:

`res/layout/textsize.xml`:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~xml linenumbers
&lt;LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/LinearLayout1"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" &gt;

    &lt;TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="14dp" /&gt;

    &lt;TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="14dip" /&gt;

    &lt;TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="14sp" /&gt;

    &lt;TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="@android/dimen/mysizedp" /&gt;

    &lt;!-- Small --&gt;

    &lt;TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="10sp" /&gt;

    &lt;ImageView
        android:layout_width="wrap_content"
        android:layout_height="6.5sp" /&gt;

    &lt;!-- No warnings: wrong attribute, size == 0, etc --&gt;

    &lt;TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="0sp" /&gt;

    &lt;TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:marginTop="5sp" /&gt;

    &lt;TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="11sp" /&gt;

&lt;/LinearLayout&gt;
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

You can also visit the
[source code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-tests/src/test/java/com/android/tools/lint/checks/PxUsageDetectorTest.java)
for the unit tests for this check to see additional scenarios.

The above example was automatically extracted from the first unit test
found for this lint check, `PxUsageDetector.testSpWarnings`.
To report a problem with this extracted sample, visit
https://issuetracker.google.com/issues/new?component=192708.

(##) Suppressing

You can suppress false positives using one of the following mechanisms:

* Adding the suppression attribute `tools:ignore="SpUsage"` on the
  problematic XML element (or one of its enclosing elements). You may
  also need to add the following namespace declaration on the root
  element in the XML file if it's not already there:
  `xmlns:tools="http://schemas.android.com/tools"`.

  ```xml
  &lt;?xml version="1.0" encoding="UTF-8"?&gt;
  &lt;resources xmlns:tools="http://schemas.android.com/tools"&gt;
      ...
      &lt;style tools:ignore="SpUsage" .../&gt;
    ...
  &lt;/resources&gt;
  ```

* Using a special `lint.xml` file in the source tree which turns off
  the check in that folder and any sub folder. A simple file might look
  like this:
  ```xml
  &lt;?xml version="1.0" encoding="UTF-8"?&gt;
  &lt;lint&gt;
      &lt;issue id="SpUsage" severity="ignore" /&gt;
  &lt;/lint&gt;
  ```
  Instead of `ignore` you can also change the severity here, for
  example from `error` to `warning`. You can find additional
  documentation on how to filter issues by path, regular expression and
  so on
  [here](https://googlesamples.github.io/android-custom-lint-rules/usage/lintxml.md.html).

* In Gradle projects, using the DSL syntax to configure lint. For
  example, you can use something like
  ```gradle
  lintOptions {
      disable 'SpUsage'
  }
  ```
  In Android projects this should be nested inside an `android { }`
  block.

* For manual invocations of `lint`, using the `--ignore` flag:
  ```
  $ lint --ignore SpUsage ...`
  ```

* Last, but not least, using baselines, as discussed
  [here](https://googlesamples.github.io/android-custom-lint-rules/usage/baselines.md.html).

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